
When migrating Orders from Magento to Shopify, additionally you can also migrate the history of Comments.
To do that, include the table “sales_flat_order_status_history” on Magento 1.x or “sales_order_status_history” on Magento 2.x export to CSV file from the Magento database, along with all the other tables.
Read the full tutorial on how to migrate Orders from Magento to Shopify.